treewide: Replace the usage of PIPE_SHADER_* enum values with MESA_SHADER_* enum values and rename gl_shader_stage to mesa_shader_stage
As enum pipe_shader_type are getting more complicated after !23291 (merged)
This is a partial rework of !17760 Only did the rename and did not remove any redundant code. Just the pipe_shader_type are simplified and renamed to mesa_shader_stage.
The redundant code removal in !17760 can be redo based on this MR
NOTE: each commits can be compiled(tested locally) so we can merge the commits one by one